1. Field of the Invention
The present invention relates to an ankle-foot orthosis made integrally from a thin, shaped lightweight material. Such orthosis is used for supporting the foot of a patient suffering from neurological disorders due to cerebral haemorrhage, tumours, radiation treatment or diseases, so that the patient may achieve an almost natural and dynamic gait.
2. Description of Prior Art
U.S. Pat. No. 5,897,515 discloses an orthosis of this kind made from carbon fibre reinforced plastic resin. The known orthosis comprises a foot plate for supporting the foot of the user and a frame part extending upwardly from the foot plate in front of and in contact with the tibia area of the leg of the user.
It is an object of the present invention to improve this known orthosis.
Thus, the present invention provides an ankle-foot orthosis made from a thin, shaped lightweight material and comprising a flat foot-supporting member for extending beneath the sole of a foot of a user, a calf abutment member for abutting the calf of the user, a narrow connecting member extending from the foot-supporting member at a location on one sidexe2x80x94preferably the outer sidexe2x80x94of the ankle of the user to the calf abutment member so as to interconnect the foot-supporting member and the calf abutment member without contacting the tibia area, and a releasable fastener for fastening the calf abutment member to a leg of the user.
Because the orthosis according to the invention does not comprise parts covering the front part or the tibia area of the leg of the user the orthosis according to the invention is less visible in use than the prior art devices. This feature is especially important when a female user wears a gown or skirt and uses the orthosis at the same time. Furthermore, the orthosis according to the invention is more comfortable in use than the orthosis disclosed in the above U.S. patent. The reason is that the known orthosis relies on contact with the tibia area, which is often tender or painful.
Preferably, the connecting member is connected to an arch part of the foot-supporting member at a location adjacent to the arch of the foot of the user and in front of the lateral malleole. From this position the narrow connecting member extend to the calf abutment member without passing the anterior or front side of the leg of the user. Thus, the connecting member preferably extends along a substantially helical path.
The connecting member is preferably relatively thin, narrow and stiff, while the calf abutment member is relatively broad and defines a relatively large abutment surface. Therefore, the narrow connecting member is preferably widening towards the calf abutment member, which is arched so as to define a calf abutment surface being substantially complementary to the shape of the calf of the user.
The releasable fastener used for fastening the orthosis to the leg of the user may be of any suitable kind and may, for example, comprise a skin adhesive, a clamp or the like. In the preferred embodiment the releasable fastener comprises a strap for interconnecting opposite ends of the calf abutment member. Thus, the calf abutment member and the strap may encircle the crus of the user, and tightening the strap may fasten the orthosis. The strap may be held in position for example by means of a Velcro fastener.
The orthosis according to the invention may be made from a thin material, such as sheet metal or plastic material. In the preferred embodiment, however, the orthosis is made from fibre-reinforced thermoplastic material. This allows for a lightweight and strong structure, and yet the form of the orthosis may to some extent be adapted to the individual user when the thermoplastic material is heated to a softening temperature. The reinforcing fibres may be of any type conventionally used in plastic materials. Preferably, carbon fibres, glass fibres or a combination of such fibres are used. The reinforcing fibres may form strands, layers or cloths. In these layers the fibres may extend in the same general direction, in two crossing directions or may be randomly distributed.
The arch part of the foot-supporting member may be located between a rear or a heel supporting part and a front or ball supporting part of the foot-supporting member, and the heel supporting part is then preferably more flexible than the ball supporting part. This may, for example, be obtained by including more layers of reinforcing fibres in the ball supporting part than in the heel supporting part. By varying the flexibility of the various parts of the foot-supporting member the user may obtain a more natural gait.
While it is important that the foot-supporting member is flexible the object of the connecting member is to maintain the foot-supporting member and the calf abutment member in a substantially fixed mutual position. Therefore, the connecting member is preferably substantially more stiff than the foot-supporting member. This may, for example be obtained by including more layers of reinforcing fibres in the connecting member than in the heel and ball supporting parts of the foot-supporting member.
At least some and preferably all of the layers of reinforcing fibres extending longitudinally within the connecting member may continue into the arch part of the foot-supporting member. This provides a good mutual connection between the connecting member and the foot-supporting member and also provides a desired reduced flexibility of the arch part.
The thermoplastic material forming the matrix material in which the reinforcing fibres are embedded is preferably one or more of the following materials: polyethylene, polypropylene, modified polyethylene terepthalate, polyamide, polyethylene terepthalate, polyether imide, polyether sulfone, and polyether ketone.
The orthosis according to the invention may be an undivided, unitary member. Alternatively, the orthosis may be made in two or more parts, which are subsequently interconnected permanently or releasably. As an example, the narrow connecting member may be divided into two parts, which are releasably interconnected, for example by means of a connecting member embracing adjacent ends of the said two parts of the narrow connecting member.
The connecting member may be adapted to allow the length of the narrow connecting member to be adjusted.
According to a further aspect the present invention provides a method of making an orthosis as described above, said method comprising positioning the thermoplastic materialxe2x80x94preferably in the form of fibres, films, granules, or the likexe2x80x94and the reinforcing fibres between opposite plastic films or foils in a desired mutual arrangement, sealing the space defined between the opposite films, removing air or gas from said sealed space so as to compact the material arranged therein and form a blank. Subsequently, the blank thus formed may be formed into a desired shape, for example in a mould. This shape may be retained by heating the blank to a plasticizing temperature and subsequently cooling the shaped article thus formed. Preferably, such heating and cooling takes place while the shaped article is still within the mould. The said plasticizing temperature is preferably sufficiently high to allow the reinforcing fibres to become embedded in the plasticized thermoplastic material forming a matrix material.
The melting point of the films enclosing thermoplastic material and the reinforcing fibres may have a melting point being higher than the melting point of the thermoplastic material forming the matrix material. In that case the opposite films may form an outer skin layer of the finished orthosis. If, however, the melting point of the films is equal to or lower than that of the thermoplastic material positioned therebetween the material of the films may migrate into or become combined with the thermoplastic matrix material.
The air or gas may at least partly be removed from the sealed space between the opposite films, when positioned within the mould so as to remove residual air or gas or gas released during heating the thermoplastic material. Thus, the blank may be positioned in a mould cavity defined between a pair of first and second mould surfaces. The first mould surface defining the desired shape may be formed by a relatively stiff mould wall, while the second mould surface may be formed by a flexible wall and the mould cavity may then be connected to a vacuum source so as to form the blank into the desired shape.
Alternatively, a blank or pre-form formed by fibres and thermoplastic material may be arranged within a mould cavity defined between a pair of separable mould parts. When the pre-form or blank has been positioned in the mould cavity and heated to a plasticizing temperature the mould parts defining the desired shape of the final orthosis are pressed together so as to force the pre-form to adopt the shape defined by the mould cavity surfaces. At least one of the mould parts may be made from an elastic or resilient material, such as silicon rubber.
In any of the methods for making the orthosis, in which the blank or pre-form is heated, such heating may at least partly be obtained by placing electrical conducting material within the blank or pre-form and by sending electric current through the conducting material. Such conducting material may comprise reinforcing fibres, such as carbon fibres arranged within the blank or pre-form.